By the time she was 22 and her modeling career was at its peak, Valletta was abusing cocaine and alcohol.

"I had a multimillion [dollar] deal and I showed up the first day to shoot this campaign high and drunk," she admits. "I didn't care and that's just to show you addiction takes you to the worst places."

The Oklahoma native says the modeling industry contributed to her disease. "I was in a business that drugs and alcohol were widely acceptable and they were given to me."

But she takes full responsibility for her actions. "I am not a victim," she says. "I don't blame anything that happened to me that was negative."

Valletta sought help at 25 because she "didn't want to die."

"I had to be willing to lift the veil off the shame and say, 'I'm an addict, I can't do this alone, I don't want to do this alone, I don't feel comfortable, can you help me?' "

After staying sober for 15 years, the model-turned-actress – whose new show Legends premieres on TNT in August – hopes to inspire others by sharing her story.

"My hope is that someone, somewhere in this room, out of this room will hear something that will help them and perhaps get them out of the shadows and the darkness of addiction and bring them into the light."